What can you do to keep it from happening though? It's not like you can just grab their brain and make them apply themselves.

I would hazard to guess in tech this role is being filled up by coder bootcamps and Pluralsight, if such candidates were aware of any knowledge deficiencies.

Unless the problem is that your years of actual experience with the actual technologies being taught in these camps is frowned upon by recruiters in favor of people completing them because they have completed some camp and you have not..

Yes, some people are sloppy and never learn, that doesn't mean that others arent self motivated and learn these things without needing someone to spoon feed them through a bootcamp...